Sensor modules are known, for example light sensors, comprising a plurality of submodules arranged alongside one another to provide an array. Each submodule comprises, for example, a die of semiconductor material housing an electronic device, for example, a light-sensor device.
A conventional sensor module in the form of an array may be formed on a substrate (previously machined and comprising a plurality of electronic devices and/or electrical connections or pads) or on a printed-circuit board (PCB) by arranging a plurality of dies alongside one another for providing a sensitive module of larger size. Each die is arranged at a minimum distance from the other dies to minimize occupation of area and increase as much as possible the resolution of the sensor module as a whole, in accordance with the manufacturing tolerances. However, one of the main reasons for occupation of useful area is linked to the fact that each die is generally surrounded by a plurality of electrical-connection pads provided on the substrate and used for enabling an electrical connection between the die and the substrate itself. The electrical connections between the pads and each device are generally provided by means of wire-bonding techniques so as to enable electrical connection of each pad present on the substrate or PCB with a respective pad present on the device.
The presence of the pads on the device and on the substrate (or likewise on the PCB) and of the wires for electrical connection between them may cause a considerable occupation of area, with consequent increase in the dimensions of the final module, reduction of the fill factor (sensitive area/total area) and loss of resolution.
In order to partially overcome this problem, it may be possible to form vertical connections by forming deep trenches from the back of the substrate until the opposite surface, where the conductive pads are provided, is reached. Said vertical connections, filled with conductive material, are then used for providing the electrical connection between the front of the die and, for example, a printed-circuit board on which the die is mounted. In this way, a region of the printed-circuit board surrounding the die is recovered.
However, even though the latter approach reduces the occupation of area enabling a greater lateral approach between the dies arranged on the printed-circuit board, an increase in the fill factor is not guaranteed. The vertical connections, in fact, occupy a portion, that may prove significant, of the active area of each die. Said occupied portion often cannot be used for the purposes envisaged (for example, detection of light in the case of dies housing a light sensor). What has been said is evident from FIG. 1, which shows, in top plan view, a portion 7 of a wafer on which a plurality of sensor devices 1 are provided, for example, light-sensor devices. Each sensor device 1 comprises an active-area region 5, comprising a plurality of vertical conductive connections 3, also known as through silicon vias (TSVs). The useful active area is indicated in FIG. 1 with a dashed line and designated by the reference number 2, and has an extension visibly smaller than the total active area 5 on account of the presence of the TSVs.
Each sensor device 1 is separated from the other sensor devices 1 on the wafer by respective safety regions 6. At the end of the steps for manufacturing the sensor devices 1, the latter are separated from one another by means of a dicing step. Dicing is carried out along scribe lines 4 (ideally indicated in the figure with a dashed line) within the safety regions 6. The safety regions 6 have a function of preventing the sensor devices 1 from undergoing damage during the process of dicing of the wafer.
At the end of the dicing step a plurality of dies is obtained, each of which includes a single sensor device 1.
From FIG. 1 it is evident how the plurality of conductive connections 3 may cause a significant reduction of useful sensitive area with respect to the total surface of each die.